1. Field of the Invention
The present invention relates to network device testing equipment for testing network devices used in a network and related fields including Ethernet communications and Internet.
2. Description of the Prior Art
To filter out computer viruses or unwanted URLs (Uniform Resource Locators) in the network, it is necessary to confirm both the filtering function and the filtering performance that discriminates packets to be blocked and packets not to be blocked. In particular, the behavior of the network device is important when having received a DoS attack (Denial of Service Attack) that is known for modifying the function return address to invade by perpetually sending small-sized packets until the packet buffer overflows.
Personal computers are often used in equipment for testing network devices taking advantage of its versatility and the communication function installed in it. The equipment suffers restrictions from MAC (Media Access Control layer: a layer for controlling transmission and receipt of frames reciprocated through a network) chips in controlling network protocols. Such restrictions cause problems in high load tests using a small packet. In testing a filtering apparatus, it is necessary to count packets that fail to pass while desired to pass and packets that pass while desired to be filtered out. In the testing, some cautions have to be paid for arrival sequence of the packet desired not to be filtered out, because the arrival order is possibly changed by the filtering apparatus. When all packets transmitted are recorded and compared with the received packets, the functions of the filtering apparatus can be examined. However, the following problems are imposed.    (P1) The required memory size for recording the packets becomes huge.    (P2) A separate communication channel having the same bandwidth as the Ethernet path to be examined is required for transferring the transmitted packet data to the examination section of the receiver.    (P3) The procedure to compare the transmitted packets with the received packets requires a large scale of circuits and is time-consuming.
In the conventional technique using a personal computer, particularly in the case of small-sized packets, the testable communication speed (throughput) is not sufficiently high to test at full media speed (speed of the physical layer of a network, the Ethernet includes the standards using an electric wire or optical fiber of 10 Mbps, 100 Mbps, 1 Gpbs and 10 Gpbs). Though there is a performance measuring apparatus using ASICs (Application Specific Integrated Circuits) for a network device, since specifically designed chips are required, the performance measuring apparatus is inclined to be very expensive in spite of low degree of freedom of the test items.